1. Field of the Invention
The present invention relates to a tuner unit apparatus which receives digital TV (television) signals and analog TV signals.
2. Description of the Related Art
Conventionally, there is a known tuner unit apparatus for receiving TV signals provided with a tuner which has a function to receive both digital TV signals and analog TV signals. There is also a known tuner unit apparatus which is further provided with a main controller and a sub controller so that the main controller and the sub controller control an operation of receiving TV signals in the tuner by I2C (inter-integrated circuit) communication.
In contrast, there is another known tuner unit apparatus provided with a tuner which has a function to receive both digital TV signals and analog TV signals. This tuner unit apparatus has a bus switch to switch between a digital reception control line and an analog reception control line, and the analog reception control line is connected to the bus switch via a MOSFET (metal-oxide semiconductor field-effect transistor) (refer to Japanese Laid-Open Patent Publication No. 2008-271290, for example). There is also a known tuner for satellite broadcasts which is provided with a first signal processing circuit for processing analog FM (frequency modulation) signals and a second signal processing circuit for processing digital QPSK (quadrature phase shift keying) signals. In this tuner, either the first signal processing circuit or the second signal processing circuit is switched ON, and other is switched OFF (refer to Japanese Patent Publication No. 3,504,847, for example). There is also a tuner unit apparatus which has a switching circuit which selectively switches between video signals and specific screen signals in a front end of a superposed circuit (refer to Japanese Utility Model Registration No. 3,052,682, for example). Moreover, there is a known tuner unit apparatus which receives TV signals of NTSC (National Television System Committee) system and TV signals of ATSC (Advanced Television System Committee) system. This tuner unit apparatus has plural switches for switching electrical power supplied to plural processing circuits ON and OFF separately and a switch for switching between destinations of received signals (refer to Japanese Laid-Open Patent Publication No. 2006-140846, for example). Moreover, there is also a known tuner unit apparatus which has a function to receive both digital TV signals and analog TV signals to stop forming an operation clock in a front end when receiving the analog TV signals so that the front end is switched to sleep mode (refer to Japanese Laid-Open Patent Publication No. 2008-135973, for example).
In the conventional tuner unit apparatus described above, when the sub controller controls an operation in a control object other than the tuner (a DAC (digital analog converter) which converts digital signals to analog signals, a scaler IC (integrated circuit) to convert resolution, an input-output selector for input-output selection of signals to an external equipment, a slicer IC to process EPG (electronic program guide) data, and a sound multiprocessing circuit to multiplex a sound, for example) while the main controller controls an operation of receiving the TV signals in the tuner, a communication by the main controller and a communication by the sub controller interfere with each other. As a result, the operating control of receiving the TV signals in the tuner by the main controller and the operating control in the control object other than the tuner by the sub controller cannot be simultaneously carried out.
Moreover, also when the main controller controls an operation in a control object other than the tuner while the sub controller controls an operation of receiving the TV signals in the tuner, a communication by the main controller and a communication by the sub controller interfere with each other. As a result, the operating control of receiving the TV signals in the tuner by the sub controller and the operating control in the control object other than the tuner by the main controller cannot be simultaneously carried out. Even when applying the matters disclosed in the above patent documents, the above problem cannot be solved.